Semi-insulating Polycrystalline Silicon Films Research Articles

Formation of Si nanocrystals in LP CVD semi-insulating polycrystalline silicon films

Influence of oxygen on silicon nanocrystals formation peculiarities and size in semi-insulating polycrystalline silicon thin films has been demonstrated by the means of local atomic surrounding sensitive electronic structure experimental studies. Low-pressure chemical deposition from the gas phase at a relatively low temperature leads to formation of semi-insulating polycrystalline silicon film containing nanocrystals with the grain size of 20–40 nm. At the same time, films oxygen doping result in formation of silicon nanocrystals arrays with the mean particle size less than 10 nm. Possibility of size-controlled Si nanocrystals formation followed by electronic structure reconstruction of amorphous films with nanocrystalline inclusions is discussed and can be found prospective for a range of possible applications.

Improved Planar MOS Barrier Schottky (PMBS) Rectifier with High-<i>k</i> Dielectrics

In this paper, an improved planar MOS barrier Schottky (PMBS) rectifier is proposed which utilizes the PECVD deposited high-k semi-insulating polycrystalline silicon (SIPOS) as the MOS area gate dielectrics for the first time. By adopting the high-k SIPOS as the MOS gate dielectrics, the peak electric field at the interface betwwen dielectrics layer and SiC can be significantly relieved and the device reliability can obviously enhanced without considerable degradation of on-state characteristics. With the optimized the thickness of the SIPOS film, the breakdown voltage (BV) of 1500V for the fabricated device was achieved, which is approximately corresponds to 85% of the theoretical parallel plane breakdown voltage value calculated from the used epilayer structure. And the specific on-state resistance (RSP-ON) is about 4.2mΩ•cm2. The corresponding figure-of-merit of VB2/ RSP-ON for the proposed device is 535.7MW/cm2.

Initial stage of semiinsulating polycrystalline silicon film growth

An experimental investigation is conducted into the initial stage of deposition for semiinsulating polycrystalline silicon (SIPOS) versus undoped polycrystalline silicon, with the N2O-to-SiH4 flow-rate ratios ranging from 0 to 0.23. It is shown that adding N2O to SiH4 does not change the pattern of the process. The initial stage is found to consist of a period of island growth followed by a period of coalescence, ending with the formation of a continuous film. Islands arise with a horizontal size of up to 95 nm. The minimum thickness of a continuous film is about 5 nm for SIPOS as against 22 ± 4 nm for undoped polycrystalline silicon.

Improving reliability of beveled power semiconductor devices passivated by SIPOS

Semi-insulating polycrystalline silicon films were prepared by direct current glow discharge on bevelled power semiconductor devices. Devices passivated by polyimide were also fabricated for comparison studies. The reverse current–voltage characteristic was studied at room temperature and high junction temperature. The differences arose from the remnant unbalance charges in the passivants as well as the varying dielectric strengths. Passivation materials applied to the beveled devices played a key role in achieving the targeted voltage. Results obtained indicated that the performance of power semiconductor devices passivated by SIPOS were superior to those passivated by polyimide, and SIPOS based process was effective and expected to enhance the reliability and yield.

Non-stoichiometric silicon oxide deposited at low gaseous N 2O/SiH 4 ratios

Semi-insulating polycrystalline silicon films were deposited using different N 2O/SiH 4 ratios, different pressures, at 650 and 700 °C, in a low-pressure chemical vapor deposition furnace. The deposition rate of the films increased with increasing pressure, increasing temperature and decreasing N 2O/SiH 4 ratio. At higher N 2O/SiH 4 ratios, more oxygen is incorporated in the film. Oxygen rich films had lower conductivities and lower dielectric constants than silicon rich films. The annealing of the films, at only 430 °C, decreased the conductivity indicating that more silicon-oxygen bonds are formed. The films also proved to be photoconductive.

Depth inhomogeneity of deposited thin films: application to semi-insulating polycrystalline silicon films

The depth inhomogeneity of semi-insulating polycrystalline silicon (SIPOS) films was studied in dependence on oxygen concentration by optical measurements and Auger electron spectroscopy. It is shown that the degree of inhomogeneity of the investigated films increases with rising oxygen content in the SiO x mixture. The influence of the refractive index gradient on the accuracy of thickness determination is also discussed.

Influence of oxygen concentration on optical properties of semi-insulating polycrystalline silicon films

Optical properties of semi-insulating polycrystalline silicon (SIPOS) films were investigated over the wide region of wavelengths. The vibrational modes of Si-O-Si and Si-Si bonds were studied by IR and Raman spectroscopy. A pronounced effect of oxygen content on the measured spectra was observed. Optical constants of SIPOS films have been compared with those of amorphous silicon and glassy silicon dioxide and their values have been successfully interpreted in terms of the theory of effective medium. The results have shown that the amorphous character prevails in the as-deposited SIPOS films.

Influence of oxygen concentration on optical properties of semi-insulating polycrystalline silicon films

Influence of oxygen concentration on optical properties of semi-insulating polycrystalline silicon films

Characterization by x-ray photoelectron spectroscopy of the chemical structure of semi-insulating polycrystalline silicon thin films

The x-ray photoelectron spectroscopy (XPS) technique has been used to investigate the composition of semi-insulating polycrystalline silicon (SIPOS) films having oxygen contents of 10 and 35 at. % prepared by low pressure chemical vapor deposition. XPS analysis has demonstrated that the film compositions can be qualitatively described by means of the five Si-SixO4−x tetrahedra (with 0≤x≤4 and integer) predicted by the statistical random bonding model (RBM). However, the quantitative analysis of the XPS spectra has demonstrated that the concentrations of the various tetrahedra found in the SIPOS films are remarkably different from those predicted by a statistical approach, i.e., by assuming that each Si atom forms with equal probability bonds with either Si or O. We have also found that the composition of high temperature (up to 1000 °C) annealed films further departs from that predicted by the RBM model; indeed, the anneal promotes the decomposition of partially oxidized Si-SixO4−x tetrahedra in Si-Si4 tetrahedra (that form Si nanocrystals) and Si-O4 tetrahedra (that enrich the oxygen content of the amorphous phase).

Semi-Insulating Polycrystalline Silicon by Low Pressure Chemical Vapour Deposition from Disilane and Nitrous Oxide

Usually, semi-insulating polycrystalline silicon films SiOx are obtained from the chemical decomposition of silane and nitrous oxide. In this paper we describe the study of semi-insulating polycrystalline silicon (SIPOS) films from disilane and nitrous oxide by low pressure chemical vapour deposition. The kinetics of growth and the variation of oxygen content have been investigated relatively to deposition parameters such as temperature, total pressure and gas flow ratio. The oxygen content is assessed by X-ray photoelectron spectroscopy (XPS) and by differential thickness method. We show that the growth rate is higher for “disilane SIPOS films” than “silane SIPOS films” and we explain this behaviour by the strong difference in growth rate of silylene species. We also show that the inhibition effect of nitrous oxide on the growth rate is very low in the case of SIPOS films obtained with disilane. The electrical resistivity depends on the oxygen content and is ranged between 109 and 1013 Ω· cm.

The Conduction Mechanism of Semi-Insulating Polycrystalline Silicon Films

physica status solidi (a)Volume 147, Issue 1 p. K17-K20 Short Note The Conduction Mechanism of Semi-Insulating Polycrystalline Silicon Films W. K. Choi, W. K. Choi Microelectronics Laboratory, Department of Electrical Engineering, National University of Singapore Search for more papers by this author W. K. Choi, W. K. Choi Microelectronics Laboratory, Department of Electrical Engineering, National University of Singapore Search for more papers by this author First published: 16 January 1995 https://doi.org/10.1002/pssa.2211470135Citations: 4 10 Kent Ridge Crescent, Singapore 0511. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume147, Issue116 January 1995Pages K17-K20 RelatedInformation

Energy distribution of grain boundary traps in semi-insulating polycrystalline silicon films doped with oxygen

The energy distribution of the grain boundary traps in semi-insulating polycrystalline silicon (SIPOS) films prepared by low pressure chemical vapor deposition (LPCVD) is determined for various oxygen contents taking account of the segregation effect of phosphorus. The energy distribution of the grain boundary traps is expressed as a Gaussian distribution. The surface trap density of the grain boundary and the energy band gap of the films increase with increasing oxygen content. Both peaks of the energy distribution of the donor- and acceptor-type traps are located at 0.49 eV over the valence band in case of poly-Si films, but moves toward the midgap as oxygen content increases in case of SIPOS films.

Influence of oxygen concentration and annealing on morphology and electrical properties of semi-insulating polycrystalline silicon

Semi-insulating polycrystalline silicon films, deposited by low-pressure chemical vapor deposition on oxidized Si substrates at O concentrations from 2 up to 35 at. % O, have been annealed at 920 °C for 30 min. Transmission electron microscopy revealed the presence of crystalline Si grains. The average Si grain radius decreases with O content going from ≊15 up to ≊2 nm, while electrical resistance increases with O concentration of almost four orders of magnitude. We attribute the resistance increase at large O contents to the presence of SiO2 shells, two monolayers thick, covering the Si grains. At these large O contents a noticeable increase in Si grain size and electrical conductance is observed in samples annealed at 1200 °C for 30 min. These results can be interpreted on the basis of thermal instability of the oxide shells. This assumption is supported by observations of native oxide breaking against high-temperature annealings.

Study on the optical absorption of oxygen-doped polysilicon thin films

Optical absorption measurements were used to study the optical properties of semi-insulating polycrystalline silicon (SIPOS) with different levels of oxygen dopings and a variety of annealing conditions. The optical properties of SIPOS were found to be closely related to the SIPOS microstructure. The absorption coefficient in SIPOS films with a high oxygen content displays a blue shift. From the absorption edge measurements, it has been observed that more band-tail states were introduced forthe higher oxygen contentsamples. During the heat-annealing processes, changes occur in the absorption spectra of SIPOS: the absorption coefficient of SIPOS displays a blue shift, whereas after high-temperature (<i>T</i> > 900°C) treatments, the absorption coefficient of SIPOS shows a red shift. These features of the optical properties of SIPOS are interpreted as the contribution of the distribution of Si-O bonds in the films and the recrystallization of SIPOS during low-temperature and high-temperature annealing processes, respectively.

High-voltage planar devices using field plate and semi-resistive layers

An improved high-voltage technique based on the use of a field plate combined with semiresistive layers (SIPOS) on oxide is proposed. The field plate and SIPOS (semi-insulating polycrystalline silicon) are shown to have complementary functions. Junction curvature electric field effects are reduced by the presence of the field plate. The silicon surface potential is linearized by a primary SIPOS layer on oxide, thereby reducing the peak electric field at the edge of the field plate. A second high-resistivity SIPOS layer provides an excellent passivation, and also prevents the dielectric breakdown of the underlayer SIPOS film. Moreover, the savings in chip area is about 20% compared to the standard mesa termination. The global yield is 94% for the SIPOS planar transistors and 86% for equivalent devices in mesa technology. The complete fabrication, design, electrical characteristics, and reliability of high-voltage planar transistors are described. >

The effect of an interfacial layer on the blocking behaviour of mesa high-voltage power devices passivated by semi-insulating polycrystalline silicon films

The breakdown voltage of mesa high-voltage power diodes was studied in dependence on the thickness of a tunnelling oxide layer introduced between the silicon substrate and the semi-insulating polycrystalline silicon film (SIPOS). A further improvement of the breakdown voltage was observed by the deposition of additional dielectric layers. The observed values of the breakdown voltage could be related to the effective density of fixed charges at the SIPOS-tunnelling oxide-silicon interface determined by high frequency capacitance-voltage technique.

Composition and structure of semi-insulating polycrystalline silicon thin films

Abstract The structural properties of semi-insulating polycrystalline silicon (SIPOS) are reviewed. The models derived from physical examinations have been used as the basis for physical models of electrical conduction, and two possibilities have emerged. Either the material is viewed as a continuous network of amorphous silicon with oxide regions interspersed or, vice versa, an oxide network with silicon regions interspersed. In order to establish which model is correct, we have examined SIPOS films containing between 7 and 51 at.% oxygen. Rutherford backscattering and X-ray photoemission are the main tools employed. Both as-deposited films, and films annealed such that changes in crystallinity are observed, have been examined and the following conclusions drawn: SIPOS containing less than about 30 at.% oxygen is mainly amorphous silicon with oxide islands and crystallization of the silicon is evident after annealing at 900°C; SIPOS containing more than 38 at.% oxygen is mainly amorphous silicon oxide co...

On the blocking behaviour of mesa high voltage power devices passivated by semi-insulating polycrystalline silicon films

The influence of the parameters of semi-insulating polycrystalline silicon (SIPOS) deposition on the reverse characteristic of mesa high voltage devices is investigated. SIPOS films deposited at 650 and 700 °C are superior to films deposited at 615 °C. Hydrogen annealing up to 600 °C improves the values of the reverse characteristic. Annealing at higher temperatures results in a change for the worse with respect to the values obtained at 600 °C. Devices passivated by SIPOS, silicon nitride and silicon oxide films exhibit breakdown voltages up to 1800 V. This value corresponds to 86% of the calculated breakdown voltage of the used bulk silicon.

Electrical conduction mechanism in semi-insulating polycrystalline silicon films

A scanning Auger microprobe (SAM) has been used to measure the equipotential lines and the potential profile across semi-insulating polycrystalline silicon (SIPOS) film structures, and the electron beam parameters required to prevent charging effects and to minimize beam current relative to sample current have been determined. The conduction process in these SIPOS films was related to Frenkel generation of carriers. This field-enhanced emission from a localized state results in a field-dependent current which is added to an ohmic current. The potential profiles obtained with the SAM are in reasonable agreement with those predicted by this model. The effects of potential screening by charge at the SiO2-SIPOS interface are discussed and related to location-dependent variations in the potential profile. A zero-field conductivity of 1.4×10−6 (Ω cm)−1 was obtained for our films.

Technologies for High Voltage Devices: Field Dependent Conductivity in Semi-insulating Polycrystalline Silicon Films

Technologies for High Voltage Devices: Field Dependent Conductivity in Semi-insulating Polycrystalline Silicon Films